So I had come across this microcontroller through a friend ... and from what I read, I imagine it could be a cheaper replacement for the Arduino Mega's accuracy, in the form factor / cost of an Uno.Apparently it is mostly software compatible with Arduino, so the possibility exists that your code will work with minimal changes. AND according to the datasheet for that PIC chip (PIC32MX320F128) there is a built in RTCC, for which all you have to do is solder on a crystal (32.768 kHz, apparently).

I actually have one of those around somewhere. I almost forgot that I had it. I bought it a few years ago hoping to be able to get more accurate sun calculations on the Sun Harvester program. Since the Uno32 is a 32 bit microcontroller, I figured that it should be capable of double precision math. After playing around with it though, I realized that it was only able to do float precision. Not because of the chip, but because of the software used to upload the program to the board. (It's possible that's changed now.)

I was finally able to get more accuracy by using the Arbitrary Precision math library on the Arduino Mega, so I stuck with that since I was so burned out on working on the program.

It seems like I would have at least tried the program on the Uno32 though since I am all about cheap. I don't remember why I gave up on it, but I should try it out again. I will say this though, at the time the Uno 32 was advertised as being 100% compatible with Arduino stuff, but that certainly wasn't true. Maybe there have been some changes to the software over the years that makes things work better now.

The 3.3V should theoretically be fine for everything really, but I've never tried it on the shield so don't quote me. Voltage drop might become more of a problem if you try to run long lines from the breakout boards to the driver boards though, but I haven't done that math on that.

From my limited understanding, supposedly the Arduino libraries which should work don't use AVR-specific hardware commands. So I imagine the EEPROM-storage code would have to be adapted.With more memory, I was thinking it would be cool to have the AccelStepper library running on the Uno32, but I doubt the feasibility.

I don't know much about the math precision though. One hopes they'll have fixed that issue.

As for voltage drop, only experimenting will tell - but yeah, I'd assume that it would only be an issue for long wire runs, and level-conversion should fix that where necessary.